We propose to continue searching for ways of increasing our understanding of normal and abnormal gene expression in man by studying human somatic cells grown in tissue culture. The specific aims of this investigation include: elucidation of the biochemical and molecular mechanisms of specific inborn errors of intracellular metabolism and transmembrane transport; definition of the pathophysiologic relationships between these mechanisms and the abnormal clinical phenotype; explanation of the basis of mammalian cell differentiation using human mutant cell lines; and further evaluation of the application of somatic cell genetics to the antenatal and postnatal diagnosis of human disease. These goals will be approached by propagating skin fibroblasts, leukocytes and epithelial cells from gut, kidney and liver from normal subjects and patients with selected inherited defects of metabolism and transport. The concerted biochemical and genetic approach of those studies will include use of the following techniques: uptake of substrate by intact cells; preparation of membrane fragments for binding studies; determination of enzyme activity; purification and intracellular localization of enzymes; cloning; synchronization; and intraspecific cell hybridization. It is hoped that this investigation will provide new insights into gene localization and regulation as it yields information relevant to specific human disorders.